Evaluation of refocus flip angle for three-dimensional proton density-weighted turbo spin-echo imaging in cerebrovascular black blood MRA and comparison with three-dimensional time-of-flight MRA

The three-dimensional time-of-flight (3D-TOF), which is currently the most common acquisition technique of intracranial magnetic resonance angiography (MRA), may result in poor branch visualization due to reduced blood flow velocity. Proton density-weighted volume isotropic turbo spin-echo acquisition (PDVISTA) is less susceptible to these factors and has been reported to be useful in assessing cerebral vasospasm after subarachnoid hemorrhage. In this study, we investigated the effect of refocus flip angle (RFA) for PDVISTA on the contrast between blood vessels and background brain tissue using flow velocity phantom and clinical images, assuming the usefulness of PDVISTA in daily clinical practice. The phantom experiments showed that the contrast ratio significantly improved with decreasing RFA; however, considering the signal-to-noise ratio, RFA 80° was determined as optimal for clinical use. Visual assessment was performed on PDVISTA (RFA 80°) and conventional 3D-TOF MRA clinical images, which suggested the superiority of PDVISTA over 3D-TOF in the delineation of peripheral branches of cerebral vessels, The results suggest that PDVISTA is useful not only for subarachnoid hemorrhage patients but also in daily clinical practice. (author)